Another week, another “I Spy in the Sea to Sky…”! How many of you got this week’s riddle?
Bull Thistle (Cirsium vulgare) is an invasive species that was brought over to North America from Eurasia as a seed contaminant and can be found in abundance in the Sea to Sky region.
Bull Thistle looks very similair to native thistles, but it is much pricklier. Bull Thistle can be found growing in disturbed areas such as fields, pastures and roadsides and can grow in a wide range of nutrient and moisture conditions. Its purple flowers are 2.5 cm to 4 cm in size and the leaves are dull and prickly with white hairs on the underside. The stems have spiny “wings” that look like a continuation of the leaves along the stem, giving them a spiky look. Bull Thistle can grow up to 2 meters tall.
Bull Thistle is an aggressive weed that can out-compete native plants and form monocultures. It can reduce biodiversity, decrease forage value (when harvested with hay), can overrun clear-cuts, and restrict access to recreational sites.
Currently, Bull Thistle is under strategic control, meaning that since the species is widespread, but control measures are taken in high priority areas in the Sea to Sky region. If you choose to do some Bull Thistle control yourself, it can be done by hand-pulling small infestations (please wear gloves!) or by mowing close to the surface several times a year. Plants that are cut prior to flowering can be left aside to decompose. If they are cut post flowering, bag, seal and dispose of the waste in the household garbage stream at the landfill or transfer station. Do not compost!